1. Field of the Invention
The present invention relates to an antilock brake control method for a four-wheel drive vehicle which, includes calculating an estimated vehicle speed on the basis of a wheel speed of a wheel and a value obtained by adding an offset value to an output from a longitudinal acceleration/deceleration sensor for detecting the longitudinal acceleration or deceleration of the vehicle.
2. Description of the Prior Art
An antilock brake control method for a vehicle is conventionally known, for example, from Japanese Patent Application Laid-open No. 28045/90, which determines estimated vehicle speeds using wheel speeds and a value resulting from the addition of an offset value to an output from a longitudinal acceleration/deceleration sensor.
In such a prior art antilock brake control, an offset value on the order of +0.7 G during acceleration is added to the output from the longitudinal acceleration/deceleration sensor. This is based on the fact that the actual accelerating ability of the vehicle is on the order of +0.7 G at the maximum. However, if acceleration of the four wheels is within about +0.7 G when all the four wheels of the four-wheel drive vehicle are in their spinning states, the estimated vehicle speeds are increased by a value corresponding to the offset value and as a result, the antilock brake control is unnecessarily started, thereby producing an operational noise in the antilock brake control.